The invention relates to methods and apparatus for the automatic testing of electrical and electronic circuitry. More specifically, it may relate to testing such circuitry in integrated form. For example, the methods and apparatus to be more specifically described below can be used for applying test signals to integrated logic circuits and to determine, from the resultant outputs produced by the logic circuits, whether the logic circuits are operating correctly and, if not, which part is faulty.
In practice, logic circuits are normally connected together to form a complete circuit board which performs a specific function or functions, all the logic circuits acting together to perform that function or functions. In order to test such an arrangement, test signals may be applied to the complete circuit board. However, it is in practice also necessary to test each particular logic circuit individually to ensure that it is carrying out correctly its part of the total function. Clearly, it is not practicable to disconnect each logic circuit from the remainder of the circuitry to carry out this test, and therefore each logic circuit must be tested in situ.
An object of the invention, therefore, is to enable circuits which are all electrically connected together to be tested individually while they are still so connected.
A further object of the invention is to enable such testing to be carried out on each such circuit without causing damage to the other circuits to which it is connected.
Another object of the invention is to provide means by which test information, for controlling the testing of any particular circuit, can be stored and retrieved when needed, and if not stored, can be set up, used and then stored for use again in the future.